If you own a new 1/2-ton Chevy Silverado, then you are probably as happy as we are with ours. Powered by the LS small-block engine, these trucks achieve admirable fuel economy while still producing decent power. With a cast-iron cylinder block and aluminum heads, the latest incarnation of the ever-popular engine is the best yet. It's just too bad that only the Corvette scores the 500hp all-aluminum LS7 version of this engine, and truck owners get the wimpy 295 pony engine. Our truck, while comfortable to drive and easy on the wallet, offered very little in the fun department. Specifically, our truck wouldn't even do a burnout from a stoplight. This is just unacceptable, so we set out to fix it, without spending too many hours under the hood. After all, we drive this thing every day.
We contacted SLP Performance Parts to see what the company had cookin' for the LS engine, and it responded with a new air intake system, a Diablosport Predator ECM programmer, ceramic-coated shorty headers, and new rocker arms. We dyno'd each part individually just to see what would happen if you purchased the items one at a time, and then we also tested the whole group. The results were surprising. As a whole, the parts were worth 33.3 hp and 17.2 lb-ft of torque, but there's more to the story than that.
Our parts were part of SLP's 350hp package, which once completely installed, should have our engine producing 350 hp as measured at the flywheel, once we'd put a few miles on the truck and allowed the computer to adapt to the new parts and programming. Given the tight deadlines of a magazine, we installed everything we could on Westech Performance Group's chassis dyno in one afternoon and immediately tested the truck, without putting any miles on it. Factor in 100-degree air temperatures and the fact that we couldn't install the new, free-flowing exhaust system onto our oddball extended cab '06 model truck, and you can see why baseline dyno-testing showed the engine produced just 237.9 hp at the wheels. Given a mechanical loss of power through the drivetrain, the engine should have been producing at least 250 horsepower to the wheels to begin with. The lack of air density-corrected altitude was at nearly 4,000 feet during our test-surely took the wind out of our small-block.
After the install, the engine was still putting 271.2 hp to the wheels, which is pretty good considering the conditions and time invested. Since our truck had a 5-1/2-foot bed, instead of the standard 6-footer, the bitchen SLP exhaust wouldn't fit, and we are certain that given the data we gathered during our test there's more power to be had with this package as a whole, so we'll return to the dyno next month to find it. Now that we've given you that bit of news, here's the reason we are excited about SLP's parts: They actually give you better fuel economy.
The dyno showed off the new power, but a road test told the real story; the engine was operating much more efficiently because we picked up nearly 2 mpg on the next tank of fuel. Before the install, we averaged 17.4 mpg in traffic and the highway, and 19.2 mpg on the highway only. After the upgrades, we got 21.6 mpg with the cruise control set at 70 mph on the freeway. So, not only does this package make more power, but you are going to save cash afterward when you go another 60 miles between fill-ups.